Pbocess of cohceitteatihg oxidized obes ahd minerals



Patented Get, 2,

lclblilflifi EilFATES @FFHCE,

FRANK A. BIRD, OF SALT LAKE CITY, UTAH.

N Drawing.

This invention relates to an improved process of concentrating oxidized ores and minerals and more particularly to an improved process of preparing such minerals or ores or mixtures of minerals for flotation concentration.

It is a well known fact that the process of flotation concentration by which true sulphide ores are treated is not applicable to oxidized ores for the reason that suflicient of the oxidized mineral values cannot be recovered by such process to render the process commercially successful or practicable, and this is true even where some soluble sulphide reagent is employed to effect the deposition of a sulphide film or coating on the oxidized minerals, for the employment of such a reagent adds to the expense of the operation and, as a final result, the percentage of pos- 9O sible obtainable values recovered is so lon that the process is not commercially profitable. In referring to oxidized ores and minerals, I have reference to the sulphates, carbonates, chlorides, oxides, and other minerals, the formation of which occurs from the alteration and breaking down of the true sulphide minerals such as pyrites, galena, zinc blende, chalcopyrite, the sulph-arsenates, the sulph-antimonates, and other sulphide combinations of metals having bright untarnished surfaces which respond to the sulphide flotation process and those sulphide minerals having only a very limited superficial oxidation which may be made amenable to the said process, and, therefore, the presentinvention contemplates a process of treating such minerals or ores whereby they will be rendered amenable to flotation c011- centration, an oxidized ore, within the purview of the present invention, being one either composed entirely of oxidized minerals or in part of oxidized minerals and part sulphide minerals.

Another object of the invention is to evolve a process of preparing oxidized minerals and-ores, or ores, or mixtures of minerals, to render them amenable to flotation Application filed August 30, 1926 Serial No. 132,659.

The process ordinarily followed in treating non-complex sulphide ores for flotation concentration is substantially as follows:

The ores as received at the mill from the mine are crushed and either reduced in size by being passed through a secondary crusher or by rolls or stamps or any other suitable mechanical means, or the ores, instead of passing through the secondary crushing operation. are reduced in size by being passed through a mill having metal liners and embodying crushing or attrition elements in the nature of metallic balls or rods of iron or steel, and a. quantity of water is introduced into the mill with the ore so that the granulating process is carried on while the ore is in a moist or wet state. Ordinarily, a classifying apparatus is employed in connection with the mill and classifies the output into two portions, one of which contains the sul- H phide mineral particles in sufliciently finely granulated condition to be amenable to flotation concentration, this portion being commonly known as the pulp, and another portion in which the mineral particles are too large for flotation concentration and which portion is returned to the granulating mill for further reduction in size.

To render the pulp suitable for flotation concentration, one or more chemical reagents are introduced into the mill with the material operated'on therein, such for ex ample as lime, and if found advisable, an oil or some other flotation reagent is added. Such oil or chemical reagents are added in economical quantities at such periods in the grinding operation as may be found advisable, and to the pulp which contains the mineral particles granulated to sufficient fineness to be amenable to flotation concentration, a further quantity of oil or some other reagent conducive to flotation concentration, may be added. lowever, this process of preparation of the ore, I have discovered, possesses a marked disadvantage, namely that during the crushing or granu lating operation, the attrition of the ore particles with the metal lining of the mill and the metal balls or rods or other cri'is'hii ig or granulating parts at results in the metal of these parts being removed in a very finely divided state and, being subjected to the action of air and Water in the mill, becoming immediately oxidized, producing iron oxide, and this oxide is precipitated throughout the ore mass and coats the gangue particles with a film of iron oxide. This is true to even a greater degree where the mineral and gangrue are granulated to extreme fineness or for a longer period of time, inasmuch as a larger amountoi the metal of the mill parts is removed by attrition and, therefore, there is a greater COIltiLllllIlZltlOIl of the pulp and a consequently lower extraction of the valuable mineral content during the treatment.

Where an attempt is made to prepare an oxidized ore for flotation concentration by granulation by the process outlined above, with the intention of sul iihidizing the mineral particles either by adding a soluble sulphide to the ore during; the granulating step or operation, or by adding such a reagent to the ore delivered to the classifier to become incorporated with the pulp, or by adding such a reagent to the ore at each of these points in the apparatus, thus taking every precaution to coat the oxidized mineral particles with a sulphide film, it has been found that only a portion of the valuable mineral content can be recovered during the flotation process and, in fact, the amount is insul'licient to warrant the carrying out of the process commercially. This is due to the fact that where ores containing oxidized minerals are treated by the process, the iron oxide precipitated upon the gangue matter absorbs the sulphide or other reagent employed for sulphidizing the oxide minerals and even if a large amount of a sulphidizing reagent is added, it will continue to be absorbed. by the gangue matter in preterence to absorption by the oxidized minerals so that the coating of the mineral particles or their sulphidization is inefiiciently performed and the recovery of values is of very low percentage.

Realizing; that oxidized minerals and ores prepared by the process outlined above could not be concentrated profitably, I discovered that the dil'licnlty could be overcome by granulating the oxidized ores and minerals in a mill utterly devoid of metallic lining or any other metallic parts for acting upon the ore to granulate or reduce the same to a size suitable for flotation concentration, and in carrying out the process of treatment embodying the invent-ion,- I introduce the oxidized ores and minerals into a mill in which the granulating or pulverizing memhers are of siliceous material and in which mill there is an utter absence of any metallic lining. In this manner, the pulp delivered from the mill to the classifier is of substantially the composition of the natural mineral or ore and contains no metallic particles such that with which it is contaminated by the formerly practiced process and, of course, the deleterious formation of iron oxide is entirely avoided. As a result, the exposed surfaces of the mineral particles are capable of readily receiving the sulphide film produced by adding the soluble sulphide. or other chemical reagent and, in fact, the attrition of the ore and mineral particles with the siliceous grinding media employed in the construction of the mill serves, in effect, to prepare these surfaces, by cleansing them, to receive the film deposit. The sulphide reagent is introduced with the ore or into the receiving tank of the classifier in advance of the flotation concentrators, where it will remain in contact with the granulated ore for period of time and may be agitated, if desired, to insure of thorough contact. Of course, it may be found advisable to add the sulphide reagent or other reagent at both places in the apparatus circuit, and this will be left to the judgment of those engaged in the carrying out of the process.

The invention is, of course, not limited to the use of any particular sulphidizing reagent or other reagent for preparing the ore for flotation concentration nor to the amount in which such reagent will be employed, as these factors Will be determined by the character of the ore and good judgment.

As previously pointed out, oxidized ores,

are those originating from the decomposition and breaking down'of the true sulphide ores and if it should occur that, by this transition, substances are left remaining in the oxidized ores which are deleterious to the preparation treatment embodying; the invention, such substances may be removed, as for example by washing the ores prior to introduction into the pebble mill or other mill employing siliceous granulating members or by washing the products from the mill either as found expedient. Of course, in the latter instance, or, in other words, Where the mill product is Washed, no sulphidizing or other reagents nor any oil or other flotation reagent is added until after the washing has been completed.

Of course, where the oxidized ore to be treated by the process contains some sulphide mineral but the character of the ore warrants or necessitates its treatment by the process of the invention, the process is in no sense detrimental to the subsequent treatment of the ore by flotation concentration inasmuch as the sulphide mineral would be extracted or recovered with the oxidized mineral.

As illustrating the greatly increased recovery of the valuable mineral content from a lead ore prepared by the process of the present invention as compared with the same ore treated by the process heretofore followed, the following examples are given:

A. The ore was granulated forty minutes mg reagent.

Lead Weight Lead assay Recovery Loss Per cent Per cent Per cent Per cent Crude ore 100 7. 57 51. 31 Concentrate 8. 74 44. 44 Tailing 91. 26 4. 04

B. The ore was granulated one hour in a ball mill having metallic sides and containing metallic balls for the granulating me dium. Ten pounds of sodium sulphide per ton of ore was used for the sulphidizing reagent.

C. The ore was granulated one hour in a pebble mill having a siliceous lining and containing flint pebbles for the granulating medium. Eight pounds of sodium sulphide per ton of ore was used for the sulphidizing reagent.

Lead Weight Lead assay Recovery Loss Per cent Per cent Per cent Per cent Crude ore 100 8.30 85.2 14.8 Concentrate. 12. 45 56. 80 Tailing S7. 1.40

From the examples given it will be observed that in the first example, the loss of the lead content is nearly equal to the percentage of lead content recovered and that y in example B, the loss is even greater, due to the prolonged period of granulating and the consequent greater contamination of the ore with the iron oxide. On the other hand, it will be observed that in example C, which representsthe carrying out of the process of the invention, the percentage of lead content recovered is very high and the percentage lost is very low.

It will be understood that the process of the invention is applicable to minerals, ores, tailings, and all other metallurgical products consisting of or carrying oxidized ores or minerals.

Having thus described the invention, what I claim is:

The process of treating oxidized ores to render them amenable to concentration by the flotation process, which consists in grinding the ore in a mill free from metal surfaces with which the ore would be liable to make contact, and subjecting the ground ore to a sulphidizing agent whereby to deposit a film of sulphide thereon.

In testimony whereof I afiix my signature.

FRANK A. BIRD. [1,. s.] 

